The present application relates generally to wheels and, more particularly, to a wheel that is expandable and retractable in circumference.
Wheels used for the motion of vehicles such as automobiles, motorcycles, and bicycles and for mobile robots, gear trains, machinery, and other equipment typically have a fixed circumference. For example, in bicycles, the rim of the wheel comprises a continuous fixed band supported by a set of fixed radial spokes.
For vehicles, different diameter wheels offer different driving characteristics and performance. For example, traction is different for different sized wheels. Additionally, surfaces on which wheels travel may have different configurations and dimensions. Larger circumference wheels may not fit on the tread of a step or stair. Smaller wheels make it more difficult to navigate vertical obstacles they encounter on the ground like potholes, curbs, rocks, etc. Larger wheels also provide a smoother drive over bumps. In addition, the size wheel affects torque, acceleration, and gearing. For example, a wheel with a diameter of ten inches may be useful for climbing a tread of a stair that is twelve inches. It may be useful to extend the diameter to, e.g., double that dimension, for navigating uneven surfaces of a street or sidewalk. It would be desirable to have the ability to selectively increase and decrease the circumference of wheels, as needed.